Large scale purification of acetylcholinesterase (AChE) from bovine brain caudate nucleus tissue using affinity and molecular sieve chromatography. Separation of different molecular weight forms of the enzyme, demonstration of amino acid composition of each form. Estimation of number of active sites on each AChE form using labelled DFP. Studies on the interconversion of AChE forms and factors promoting aggregation. Investigation of the interaction between AChE and anesthetic agents including ketamine.